Scott Parazynski on being an astronaut, doctor and climbing Mount Everest

Former NASA astronaut Dr. Scott Parazynski has traveled more than 23 million miles in space over his 17-year career. He has flown five missions and conducted seven spacewalks. If that wasn't enough, he felt "compelled" to climb Mount Everest, becoming the only person to fly in space and reach the mountain's summit.

"I'd been climbing since I was about 15 years old. Just the challenge of going to the world's highest peak, I had seen it from orbit. And I took this beautiful photograph looking straight down on the summit of Mount Everest and I conjured up in my mind, 'What would it look like to actually have my boot prints down there on that beautiful summit?' And so many years later, on my second attempt, I was able to top out on the mountain," Parazynski said Monday on "CBS This Morning."

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Parazynski is out with a new memoir, "The Sky Below: A True Story of Summits, Space and Speed," where he offers an inside look at his life as an astronaut and doctor. While writing a book isn't the same kind of risk as his past explorations, Parazynski said he bared his soul in the book.

"So it's actually quite a challenge to put it all on paper, but I'm really proud of the story we're able to tell with my collaborative writer, Susy Flory," Parazynski said. "And you know, the pathway to success is nonlinear and you have to accept some failures along the way. And so I've had failures, I've had some close calls with my health as well. So by setting goals and being resolute in achieving them, you know, wonderful things can happen."

Parazynski, a personal physician for the late astronaut and Sen. John Glenn, described Glenn as "one of the greatest Americans of our time." They flew together aboard the space shuttle Discovery in 1998, when Glenn returned to orbit at the age of 77.

"It was the greatest honor of my life to be in his presence and to call him a friend and crewmate. I think the world of him. He was an incredible crewmate. He added to our knowledge of science. I miss him dearly," Parazynski said.

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Sen. John Glenn and Dr. Scott Parazynski 

Joe McNally/National Geographic for NASA